在英语语法中，不定代词后面通常可以加副词，如"something sweet"、"somewhere quiet"和"somebody reliable"。但是，有些不定代词如"anyone"、"anything"和"anywhere"不能加副词。因此，是否可以在不定代词后面加副词取决于具体的不定代词。
根据英语语法规则，不定代词后面可以加副词。例如，我们可以说：
- I want something sweet.
- He needs somewhere quiet to study.
- They are looking for somebody reliable.
在这些句子中，不定代词“something”、“somewhere”和“somebody”后面加上了副词“sweet”、“quiet”和“reliable”。
然而，也有一些不定代词不能加副词。例如，“anyone”、“anything”和“anywhere”就不能加副词。我们只能说：
- I haven't seen anyone lately.
- Is there anything else you need?
- She doesn't want to go anywhere crowded.
