Después de un sorbo de agua, me siento más tranquilo.

Después often needs de when it is followed by a noun, pronoun, or infinitive.

• después de un sorbo de agua = after a sip of water
• después de comer = after eating

If después appears on its own, the rest is just understood from context:

• Nos vemos después. = See you later / See you afterwards.

So in this sentence, de is required because it is followed by the noun phrase un sorbo de agua.

Un sorbo means a sip.

It refers to a small amount of liquid taken into the mouth. It is a masculine noun, which is why it uses un:

• un sorbo
• el sorbo

A learner may also come across:

• un trago = a drink / a gulp / a swallow, depending on context
• beber un sorbo = to take a sip

In this sentence, un sorbo de agua is a very natural way to say a sip of water.

Because Spanish often uses de + noun with quantities or measures, without the definite article, when talking about something in a general way.

So:

• un sorbo de agua = a sip of water
• un vaso de leche = a glass of milk
• una taza de café = a cup of coffee

You would use del agua only in more specific situations, such as a sip of the water:

• Tomó un sorbo del agua que estaba en la mesa.
  = He/She took a sip of the water that was on the table.

In your sentence, it is just water in general, so de agua is the natural choice.

Yes. Here the verb is sentirse, which means to feel in the sense of to feel a certain way.

So:

• me siento = I feel
• te sientes = you feel
• se siente = he/she feels

This is different from non-reflexive sentir, which often means to feel something physically or emotionally, or to regret:

• Siento frío. = I feel cold.
• Siento que algo va mal. = I feel that something is wrong.
• Lo siento. = I’m sorry.

But for describing your emotional or general state, Spanish very often uses sentirse:

• Me siento cansado. = I feel tired.
• Me siento feliz. = I feel happy.

So me siento más tranquilo is exactly the expected structure.

Both can work, but they are not exactly the same.

• Me siento más tranquilo focuses on how I feel
• Estoy más tranquilo focuses more on my state/condition

In many situations, the difference is small, and both are natural. But sentirse is especially common when talking about personal feelings from the inside.

Compare:

• Después de hablar contigo, me siento mejor.
  = After talking to you, I feel better.
• Ahora estoy más tranquilo.
  = Now I’m calmer.

In your sentence, me siento más tranquilo sounds very natural because the speaker is describing a change in how they feel after drinking some water.

Because adjectives in Spanish usually agree with the person they describe.

Here, tranquilo describes the speaker, the I in me siento. If the speaker is male, you use:

• me siento más tranquilo

If the speaker is female, you use:

• me siento más tranquila

If a group were speaking, it could change again:

• nos sentimos más tranquilos = we feel calmer (masculine or mixed group)
• nos sentimos más tranquilas = we feel calmer (all female group)

So the ending depends on who is speaking.

Más means more.

So:

• tranquilo = calm
• más tranquilo = calmer / more calm

It shows a comparison, often with the person’s previous state. In English we might naturally say I feel calmer, and Spanish expresses that as me siento más tranquilo.

You do not need to include the second half of the comparison if it is obvious:

• Me siento más tranquilo. = I feel calmer.

But you could also make it explicit:

• Me siento más tranquilo que antes. = I feel calmer than before.

Not always. It is acceptable here because Después de un sorbo de agua is an introductory phrase placed before the main clause.

So you may see:

• Después de un sorbo de agua, me siento más tranquilo.
• Después de un sorbo de agua me siento más tranquilo.

Both are understandable. The comma helps mark a pause and makes the sentence a little clearer on the page, especially with a longer introductory phrase.

In everyday writing, many native speakers would include it, but leaving it out is not unusual either.

Yes, absolutely.

Both word orders are natural:

• Después de un sorbo de agua, me siento más tranquilo.
• Me siento más tranquilo después de un sorbo de agua.

The difference is mainly one of emphasis.

• Starting with Después de un sorbo de agua highlights the time/circumstance first.
• Starting with Me siento más tranquilo puts the feeling first.

Spanish is often more flexible than English with word order, especially in cases like this.

Yes. When it is followed by a verb, that verb normally goes in the infinitive.

For example:

• Después de beber agua, me siento más tranquilo.
  = After drinking water, I feel calmer.
• Después de comer, salimos.
  = After eating, we went out.

So después de can be followed by:

• a noun phrase: después de un sorbo de agua
• an infinitive: después de beber agua

Both patterns are very common.

Yes, that is possible, but the nuance can differ slightly.

• un sorbo usually suggests a sip, often a small, careful amount
• un trago can mean a swallow, a gulp, or a drink, and can sometimes sound a bit larger or less delicate

In Spain, sorbo is a very natural and clear choice for sip.
Trago is also common, but depending on context it may sound more like gulp or swallow than sip.

So if you specifically want a sip of water, un sorbo de agua is an excellent option.