1. “A glass of water comes by request only in restaurants.”
This sentence implies that the only type of establishment in which a glass of water is served is a restaurant. However, what it means is that in a certain type of establishment, a patron must ask to be served water. To communicate the correct meaning of the sentence, structure it with that syntax: “In restaurants, a glass of water comes by request only.”
2. “She advocated as a suffragist and journalist for women to crack male-dominated careers before she became an environmentalist.”
This sentence structure suggests that the subject advocated for the stated goal, hoping that it would be achieved before she entered into her prospective line of work. But “before she became an environmentalist” is a modifier that is not integral to the sentence.
To clarify its relationship to the rest of the statement, reorder the sentence as done in the first example by getting the modifying phrase out of the way at the onset: “Before she became an environmentalist, she advocated as a suffragist and journalist for women to crack male-dominated careers.”
3. “The process is painless, and you can be an elected official by spending less than $100 in most communities.”
The implication here is that would-be politicians can succeed by investing less than $100 in each community they visit. What the writer means, though, is that less than $100 is required to file to become a political candidate.
Do you see a pattern here? A modifier invites misunderstanding when it is tacked onto the end of a sentence rather than strategically positioned. In this case, however, unlike as in the previous examples, “in most communities” does not logically belong all the way at the other end of the sentence.
Yes, perhaps the process is painless in most communities, but “in most communities” applies to the fee. That phrase should be excised from its current position and inserted not as an introductory phrase but as a parenthetical: “The process is painless, and, in most communities, you can be an elected official by spending less than $100.”