Coffee is available with no additional cost, unless you choose a "specialty" coffee (Latte and such).
Some drinks are no charge. However, Soft drinks (Sodas)and alcoholic beverages are not, unless you have the Free at Sea Beverage package included (20% cost of package value is added to your invoice, if you did select).
If you paid the Daily Service Charge, then "tipping" is not required, but very much appreciated!
Yes, you can upgrade internet onboard.