Man, I have to say - I hate upselling/ suggestive selling, but if you must - keep it discrete. If the customer looks at the food for a bit then you ask them if they're after something to eat, but you should never just say without any prompting "why not have a friand." it's forceful and agressive and most customers know it.
As for upselling coffees - I don't really understand it because we actually have a higher proffit margin on our regular coffee than our large.
Unfortunately, I work for a well known chain restaurant. I am a Univ. grad looking for a better job. I have been in the service industry for years and it has become evident to me that this and all chain restaurants are ran solely for the benefit of the shareholders with no true regards to the well being of customers and employees. ...................