Here are the corrections for each sentence:

1. **I will going to Spain next summer.**
**Mistake:** A
**Correction:** I will **go** to Spain next summer.

2. **They will to work in a pub.**
**Mistake:** B
**Correction:** They will **work** in a pub.

3. **My sister will books a hotel for next June.**
**Mistake:** B
**Correction:** My sister will **book** a hotel for next June.

4. **You will study German at university?**
**Mistake:** A
**Correction:** You will study German at university. (Change to statement or add 'will you' at the beginning for a question: **Will you study German at university?**)

5. **Sam won’t to pass his exam without working.**
**Mistake:** B
**Correction:** Sam won’t **pass** his exam without working.

So the final corrections would be:

1. A: **go**
2. B: **work**
3. B: **book**
4. A: **Will you**
5. B: **pass**