The answer is 'yes please' as long as you are happy that the operatives have worked well and have been polite and friendly - but 'tipping' with alcohol is usually frowned upon by the bosses of reputable removal companies!
The operatives will, in any case, prefer cash to beer although they will be too polite to say so!!!
The amount of the tip could reflect the time that the job takes, any difficulties encountered and if you think that the crew 'went the extra mile' for you.
Removal workers, on the whole, work extremely hard - imagine yourself having to lift and carry large sofas/heavy beds/wardrobes/badly packed (so very heavy) boxes etc through tight doorways, up stairs etc every day, including Saturdays, the favourite day for clients.
In a good company, they are actually paid quite well, though probably not as much as you may be, depending upon your job!
The overheads of a removal company are actually quite large - I am speaking as the wife of a smaller removal company owner, and the mother of one of the operatives.
Tea/coffee/water should be on offer, especially if the job takes more than a couple of hours (snacks are an added bonus!) and the client should have done their homework (via the company) about how to pack boxes, what to take ahead (kettle, tea, milk etc!) and what to expect on the day.