Poroshenko intends to discuss the terms of joint economic cooperation. Against the background of the conflict with Russia, Turkey is losing the promising Russian market. Ukraine can partially compensate for these losses.
However, the main part of the agenda will be dedicated to political issues. Both countries are in a state of cold war with Russia. Both are involved in conflicts where Russia is also participating: Ukraine in the Donbass war, and Turkey in the Syrian war. It is most likely that representatives of the two countries will discuss a joint strategy for anti-Russian actions.
This applies, in particular, to Crimea. Turkey is home to the largest Crimean Tatar diaspora, and the Crimean Tatars themselves, in language and origin, are very close to the Turks. Ukraine and Turkey could agree on joint actions with the use of this factor and, once again, could challenge the affiliation of Crimea with Russia.
According to some sources, Erdogan and Poroshenko are cooperating in Syria. Turkey is supporting the jihadists and trades with ISIS, whilst militants are receiving weapons from Ukraine. They are trafficked through Turkey.
In both cases, the strengthening of cooperation between Turkey and Ukraine in the sphere of counteracting Russia is in the interests of the United States. Both countries are being used to deter Russia.