"He buys his food and drink."
Doesn't "Il lui offre à boire..." seems to imply person A is supplying something to person B? Because "He buys his food..." certainly indicates he is buying it for himself, or that person A is buying it from person B (otherwise would be "He buys him food...). Doesn't that explain tusharbajaj opinion?
Well it's the verb "s'acheter" which is used exactly as "acheter", except that it's meant to be used when the subject buys for himself.
Here is the conjugation :
- Je m'achète * = I buy * for myself
- Tu t'achètes * = You buy * for yourself
- Il/elle/on s'achète * = He/She/it buys * for himself/herself/itself
- Nous nous achetons * = We buy * for ourselves
- Vous vous achetez * = You buy * for yourselves
- Ils/elles s'achètent * = They buy * for themselves