A relatively straightforward approach to the interpretation of (7a) and (8a) would be to extract from the corpus (via parsing) paraphrases in which the additional information (e.g., drinking and watching), which is absent from (7a) and (8a), is fleshed out.
we would like to find in the corpus sentences whose main verb is begin followed either by the progressive VP complement drinking or by the infinitive to drink, selecting for the NP coffee as its object.